Prior to the present invention, problems have existed and difficulties have been associated with the now widely used monitor. For example, in a high voltage stabilizing circuit of the monitor according to the prior art, the control transistor of the power control part may become overheated by the excessive power consumption in the transistor as the difference of power applied to the flyback transformer increases when high or low horizontal synchronization frequencies are applied to the high voltage stabilizing circuit, and the control transistor may often be damaged.